Background:Colorectal cancer is the second leading cause of Cancer death in the United States. In spite of demonstrated efficacy and guideline recommendations, colorectal cancer screening rates are low. Purpose: This study is the next step in development and validation of new instrument, the Colorectal Cancer Screening Behavior Questionnaire (CRCSBQ) to measure colorectal cancer screening participation. The long- term goal of this study is to contribute to the development of a resource of cancer screening measures with known validity across multiple settings and populations. Methods: Phase 1: The CRCSBQ will undergo cognitive testing in a sample of patients (32 total) at two geographically diverse Veterans Affairs (VA) facilities. Patients will be from the primary care clinics, over age 50 and include Caucasians and African-Americans of both genders. Phase 2: The CRCSBQ and a demographics questionnaire will be administered to 200 (total) primary care patients at the 2 sites. In addition, medical record data will abstracted from the VA electronic medical record, non-VA medical records and Medicare claims data (patients older than 65). The questionnaire responses will be compared to the medical record data. We will calculate point estimates and 95% confidence intervals for the concordance, relative sensitivity, specificity and report-to-records ratio of the CRCSBQ to detect current colorectal cancer screening status by the American Cancer Society guidelines compared to the medical record review. We will use logistic regression analysis to explore patient factors that may be associated with agreement between self-report and medical records for colorectal cancer screening. Importance: Accurate measurement of colorectal cancer screening behavior is the essential first step in studying the problem of low screening rates. Veterans followed at VA primary care clinics represent the ideal population in which to validate the new instrument. The VA health care system is the largest integrated healthcare system in the United States. There is a comprehensive electronic record which includes all inpatient and outpatient care at any VA medical center. The VA population is diverse and includes representation from a range of age groups, racial and ethnic minorities and a substantial proportion of individuals from lower socioeconomic backgrounds and lower educational levels.